1. Field of the Invention
The invention relates to the field of microelectronics fabrication. More particularly, the invention relates to the field of photoresist development during the course of microelectronics fabrication.
2. Description of the Related Art
Microelectronics devices are fabricated employing multiple layers of materials formed upon suitable carriers or substrates. Many of the layers of microelectronics materials must be patterned and registered accurately to fine dimensions. As circuit density and performance requirements have increased, the tolerances and dimensions of the patterns have become correspondingly smaller. It is common practice to form patterns in layers of microelectronics materials employing photolithography, wherein the layer of material to be patterned is coated with a light sensitive lacquer or photoresist material, which is then exposed to a pattern of light radiation to form the latent image of the pattern in the photoresist material. This latent image is then chemically developed to form a photoresist etch mask of the pattern, which can then be transferred to the underlying material layer by additive or subtractive processes such as etching or other analogous process.
The formation of increasingly finely dimensioned patterns has resulted in the need for increasingly shorter wavelength radiation to attenuate diffraction limits on the resolution of the image, and for photoresists which are capable of being exposed by such shorter wavelength radiation. Currently there is in use deep ultraviolet (DUV) radiation and excimer laser radiation which utilize photoresists sensitive to exposure to radiation of wavelengths down to about 248 nanometers (nm). The exposure of photoresist materials to such short wavelength, and hence energetic, radiation and the increasingly finely dimensioned patterns employed place stringent requirements on defect levels within the resist layers. It is necessary to minimize the amount of undeveloped material or residue left after developing the patterned photoresist layer. In the same vein, the need to remove the used photoresist layers completely without residues after processing the pattern is also a priority requirement.
Although satisfactory deep ultraviolet (DUV) photoresists are available in the form of organic linear polymers with substituent groups such as substituted phenols such as, for example, t-butoxycarbonyl (t-BOC) polymer resins formulated with photoactive materials, the use of such resists is not without problems. In many cases, it is desirable to employ photoresists which are positive with respect to image formation: i.e., such photoresists become more soluble to the developer where illuminated so that after exposure and development, the photoresist pattern is a positive image of the exposure photomask pattern. In the case of the t-BOC type resists, this is accomplished by formulating a light-absorbing additive with the resin which forms an acid upon irradiation. The acid reacts with the resin generally upon heating to split off the substituent groups and leave behind an alkali-soluble modified resin, which is then developed away by a suitable alkaline developing agent.
In such resists, any regions of exposed photoresist material which are not dissolve upon development remains in the exposed area of the pattern as a potential defect. When such residues are small with respect to typical image dimensions, they are not particularly troublesome. However, as the pattern dimensions become smaller than 0.25 micron, residues may become comparable to pattern dimensions and may be expected to adversely affect device manufacturing yields. Negative working photoresists, in which the exposed regions are rendered less soluble, also have the same potential difficulty with residues in the unexposed soluble portions of the photoresist image pattern.
It is therefore towards the goal of improved exposure and development methods for deep ultraviolet (DUV) photosensitive materials that the present invention is generally and specifically directed.
Various methods have been disclosed for improved deep ultraviolet (DUV) photoresist exposure, development and stripping.
For example, Gupta et al., in U.S. Pat. No. 5,037,506, disclose a method for improved stripping of deep UV and ion implant hardened photoresists. The method employs exposure of the hardened resist layer to anhydrous gaseous sulfur trioxide, followed by treatment in solvents such as water, alkonols, ketones and mixtures thereof.
Further, Sezi et al., in U.S. Pat. No. 5,262,283, disclose a method for forming high resolution patterns with steep edges in photoresist in the deep UV range. The method employs a resin and photoactive compound which, after exposure and treatment with an aqueous or alcohol-based solution of a polyfunctional amino- or hydroxy-silane, is then etched in an oxygen plasma to form the pattern.
Still further, Hanawa, in U.S. Pat. No. 5,429,910, discloses a method for forming an accurate vertical edged profile pattern in a conventional chemical amplification positive resist exposed with deep UV radiation. The method employs acid treatment of an exposed chemical amplification positive photoresist layer, followed by baking and subsequent development of the photoresist pattern.
Finally, Levenson et al., in U.S. Pat. No. 5,763,016, disclose a method for developing patterns in exposed photoresists either by use of a gaseous agent to accelerate the wet chemical development of the pattern or by direct development as a dry developing agent. The method employs anhydrous sulfur trioxide gas to react with an organic coating having a previously formed surface pattern or latent image pattern to render the pattern developable, either by means of wet chemical development which discriminates between patterned and unpatterned regions, or by direct removal of previously formed regions.
Desirable within the art of microelectronics fabrications are additional methods for forming and stripping deep ultraviolet (DUV) photoresist patterned layers.
It is towards this goal that the present invention is generally and more specifically directed.
It is a first object of the present invention to provide a method for forming a pattern within a photosensitive layer formed upon a substrate employed within a microelectronics fabrication with attenuated defects.
It is a second object of the present invention to provide a method in accord with the first object of the present invention, where there is enhanced the development of patterned images in photosensitive layers exposed to deep ultraviolet (DUV) irradiation, with attenuated residues within the patterned photoresist mask layer and improved subsequent stripping thereof.
It is a third object of the present invention to provide a method in accord with the first object of the present invention and the second object of the present invention, where the method is readily commercially implemented.
In accord with the objects of the present invention, there is provided a method for forming a pattern within a deep ultraviolet (DUV) photosensitive layer employed in microelectronics fabrications with attenuated defeats and improved stripping. To practice the invention, there is first provided a substrate employed within a microelectronics fabrication. Formed over the substrate is a deep ultraviolet (DUV) photosensitive layer. After selective deep ultraviolet (DUV) exposure of the photosensitive layer to form a latent image therein, there is then performed a post exposure bake of the photosensitive layer. Development of the latent image pattern is then performed employing treatment of the photosensitive layer with a first developer agent. Then a second developer treatment employing a dilute solution of the first developer agent is followed by a water solvent rinse to produce attenuated residues in the developed pattern. After drying and hard baking, the developed patterned photoresist mask layer may be employed in a microelectronics fabrication process with attenuated defects and thereafter may be easily stripped.
The present invention may be practiced where the microelectronics fabrication is selected from the group including but not limited to integrated circuit microelectronics fabrications, solar cell microelectronics fabrications, charge coupled device microelectronics fabrications and flat panel display microelectronics fabrications.
The present invention employs materials and methods as are known in the art of microelectronics fabrications, but in a novel order, sequence and arrangement. Therefore the present invention is readily commercially implemented.